Paper pulp is manufactured by treating wood in a boiling liquid at high temperatures and pressures. After the boiling process, the remaining liquid contains a number of chemicals and retains some of the wood substance, forming a “weak liquor”. In a typical mill, the water is removed from the weak liquor and a “black liquor” is obtained, and is then supplied as fuel to the recovery boiler. The recovery boiler provides a reduced atmosphere at 1000° C. to burn the remaining wood substance and release energy that is conveyed away in the form of high-pressure steam. A regeneration of the chemicals contained in the black liquor is also performed in the recovery boiler.
The black liquor is normally supplied to the recovery furnace through burners commonly referred to as liquor guns. These liquor guns often include simple nozzles provided with some form of splash or deflection plate that is mounted on the nozzle. Typically, the liquor guns are mounted for rotation about a horizontal axis, whereby the vertical position of the nozzle and deflector plate may be adjusted in order to direct the spray of the black liquor. Due to the harsh environment of the mill and recovery furnace, the entire spray gun assembly, including the tilting mechanism, must be very sturdily constructed. At the same time, the harsh environment requires that the liquor guns be serviced relatively frequently. For example, the nozzle portion of the gun projects inside the recovery furnace and is constantly exposed to high temperatures and the black liquor. Thus, the nozzles need cleaning, repair or replacement.
Accordingly, there exists a need to provide a liquor gun assembly that is not only well adapted for the harsh environment of a recovery furnace, but which also facilitates access and service of the liquor gun.